1. Field of Invention
The present invention relates to a media processing device having a media transportation mechanism that conveys media such as CDs and DVDs, and to a control method and a control program for a media processing device.
2. Description of Related Art
Media processing devices that write data and print labels on large numbers of media (information recording media) such as CD (Compact Disc) and DVD (digital versatile disc) media are known in the art. Such media processing devices typically have a media stacker (media storage unit) for storing disc-shaped media in a stack, media processing units such as a media drive for writing data to the media and a label printer for printing on the label side of the media, and a media transportation mechanism for holding and conveying the media to and from the media processing units (the media drive and label printer).
The media processing device sequentially picks the media stacked in the media stacker by means of the transportation arm of the media transportation mechanism for writing data or printing a label. As a result, the number of media stored in the media stacker gradually decreases. When no media is left in the media stacker, unprocessed blank media must be loaded into the media stacker. To eliminate wasting work time and to enable efficient media processing, the user is preferably prompted to refill the media stacker before the supply of media in the media stacker is completely depleted, such as before the last disc is processed.
To solve this problem, various methods of measuring the height of the remaining media in the media processing device have been proposed. See, for example, Japanese Unexamined Patent Appl. Pub. JP-A-2008-90966 (pages 5-10, FIG. 7). This media processing device calculates the difference between the height of the bottom when the media stacker is empty, which is stored in a storage unit (EEPROM, for example), and the height of the media stacked in the media stacker, which is measured. How many media are left in the media stacker is then determined from this calculated difference and the thickness of the media to detect when the remaining media count goes to 1.
In a media processing device according to the prior art the height of the bottom of the media stacker when empty (also referred to below as the “bottom height of the empty media stacker”) is predetermined by the design dimensions of the device and is stored in a storage unit (such as EEPROM) when shipped from the factory. However, the actual bottom height of the empty media stacker will vary between typically manufactured media processing devices because of deviation in the assembly precision and the molding precision of the component parts, as well as aging over time. The media thickness may also vary due to the type of media and surface processing.
Therefore, if the difference between the bottom height of the empty media stacker of the actual manufactured device and the value that is stored in the storage unit increases, it will not be possible to accurately detect when the remaining media count becomes 1. To solve this problem the bottom height of the empty media stacker in the manufactured products can conceivably be made more uniform between individual products by increasing the molding precision of the component parts as well as assembly precision, but this increases the production cost.
In addition, even if the bottom height of the empty media stacker is uniform at the time of manufacture, deviation from the value immediately following manufacture will occur over time due to aging.
As a result, there may actually be two (or more) media left when the remaining media count is determined to be 1. Therefore, the media processing device according to the prior art requires a step of physically checking that media is not present by attempting to pick media again after picking the media identified as the one remaining media.